I have been using the battery that came with my Treo and purchased the slightly larger, but still fit into the regular case battery from Seidio for the rare times I run out of juice. I charged both to full and put the Seidio extended one in my purse for a spare. Today, after trying a new application that will update weather every 2 hours, for the first time ever my Treo ran down to 0%. So, I popped in my extended spare only to discover it was dead.

How long should a battery hold its charge when it isn't being used? I thought it would last at least a few months. Guess I was wrong. So, what is a reasonable time to be able to count on it as a spare before I need to swap it out and use it?

Maris-
LiOn can hold a charge for over a month with nearly no loss. NiMh will lose about 30% per week, making it "dead" in 2-3 weeks. Some of the Japanese NiMh cells are much better, but the Chinese ones are useless for shelf life.
Assuming you are sure the Seidio is not a counterfeit using cheap cells--which technology is it?

Mine uncharacteristically loses power, also, and it's a genuine Seidio received straight from them. But they may well be getting their junk from China, because they clearly have problems communicating with their suppliers, and fiiguring out when "they" have succeeded in producing their extended battery. I charge mine fully and within a week it's usually down to 70% or so, pretty much the rate described above.

The problem with NiMh cells self-discharging has gotten enough publicity that a French company has brought a different cell to market under the "Hybrio" brand, IIRC. So far just the cylindrical cells for the mass market (flashlights, radios, etc.) but it shows that there are folks out there working on this problem. And expecting enough of a market on it, so that even the French would try to sell batteries in America based on beating it.<G>

I was "forced" to buy a new phone as Cingular shuts down TDMA and surcharged us all in the interim. Among the reasons I didn't want to upgrade, my old Startac took two batteries, and I had multiple LiOn spares for each, bought cheaply because StarTac stuff was around for so long and for so many phones. I'm almost tempted to see...<VBG>...

Thanks for the replies. I'm not sure what kind of battery the Sedio is as the ad says, "1300mAh High capacity" and doesn't list anything else. So, I've swapped them around and am using the Seidio as my main battery and the Palm as the backup. Maybe that will help.